This application claims the benefit of priority of Korean Application No. 10-2003-0073882, filed on Oct. 22, 2003, the disclosure of which is incorporated herein by reference in its entirety.
Generally, the present invention relates to a method for controlling an engine. More particularly, the present invention relates to a method for preventing a reverse rotation of an engine.
Reverse rotation of an engine may cause damage to various parts of the engine, including the intake manifold.
An intake manifold which receives air from a throttle valve and distributes it to intake ports in a cylinder head is usually made of a plastic or aluminum material. With regards to intake manifolds made of plastic material, some cases have been found in which the intake manifolds are damaged due to a backfire.
A typical backfire of an engine is known to occur when ignition occurs near top dead center (TDC) where a valve overlap happens, or when hot combustion gas flows back to an intake port during the overlap. However, a backfire that damages an intake manifold has been found to be caused by a reverse rotation of the engine that may happen during starting of the engine.
When an engine is stopped while in a process of starting, it may have a cylinder that is in a compression stroke at the moment of stopping. A compression pressure formed in the cylinder may push a piston toward bottom dead center (BDC), and thereby the engine may reversely rotate. In this case, when an engine speed becomes higher than a certain speed, a cylinder in which fuel has already been injected may experience ignition so the reverse rotation of the engine may be accelerated.
When an engine cycle is executed in a reverse sense from a compression stroke to an intake stroke, a compressed air/fuel mixture may flow back to an intake manifold during the intake stroke through an open intake valve. So, a first interior pressure is formed in the intake manifold. As the engine experiences further reverse rotation, the same or another intake valve may open such that a pressure is added again and again to the interior pressure resulting in damage to the intake manifold.
In addition to such damage to an intake manifold, a reverse rotation of an engine may cause further problems such as excess bearing wear.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
The motivation for the present invention is to provide a method for preventing a reverse rotation of an engine having non-limiting advantages of preventing a reverse rotation of an engine during starting.
An exemplary method for preventing a reverse rotation of an engine according to an embodiment of the present invention includes determining if a predetermined monitoring condition for monitoring a reverse rotation of the engine is satisfied, determining if an operation of a starter motor has stopped when the monitoring condition is satisfied, determining if the reverse rotation of the engine is occurring when the operation of the starter motor has stopped, and stopping fuel injection and/or ignition of the engine when the reverse rotation of the engine is occurring.
In a further embodiment, an exemplary method for preventing a reverse rotation of an engine according to an embodiment of the present invention further includes determining if starting of the engine is finished when the monitoring condition is not satisfied, wherein the determining if the predetermined monitoring condition is satisfied is executed when the starting of the engine is not finished.
In another further embodiment, the predetermined monitoring condition comprises a plurality of conditions, including, but not limited to: (1) a crank position sensor (CPS) and a vehicle speed detector are operating normally; (2) an ignition key is in an on position; (3) an engine speed is less than or equal to a predetermined reference engine speed, or a rate of change of the engine speed is less than or equal to a predetermined rate of change; (4) sufficient signals are obtained from the CPS such that cylinders may be identifiable on the basis thereof; and (5) the vehicle speed is less than or equal to a predetermined reference vehicle speed.
In a further embodiment, the reference engine speed is preset lower than a predetermined idle speed of the engine, and the predetermined engine speed rate of change is a negative value such that an engine stall may be expected in the case that the rate of change of the engine speed becomes less than the predetermined rate of change.
In another further embodiment, the reference vehicle speed is preset as a minimal value indicative of a running of the vehicle.
In another further embodiment, whether the operation of a starter motor has stopped is determined on the basis of a current battery voltage of the vehicle.
In a still further embodiment, whether the operation of a starter motor has stopped is determined on the basis of whether the current battery voltage is greater than a predetermined voltage, the predetermined voltage being lower than a battery voltage output in the case that the engine is stopped.
In another further embodiment, whether the reverse rotation of the engine is occurring is determined on the basis of intervals between adjacent signals from the CPS.
In a still further embodiment, the intervals between adjacent signals comprise first, second, and third intervals that are consecutively obtained, and whether the reverse rotation of the engine is occurring is determined on the basis of whether the second interval is greater than the first and third intervals and also greater than a predetermined reference interval.
In another further embodiment, an exemplary method for preventing a reverse rotation of an engine according to an embodiment of the present invention further includes determining a reversion-triggering cylinder which is in a compression stroke at the time when the reverse rotation of the engine is occurring.
In a still further embodiment, the determining a reversion-triggering cylinder determines the reversion-triggering cylinder on the basis of: a predetermined combustion sequence of cylinders of the engine; and TDC of a compression stroke of a reference cylinder, the TDC being determined by a reference pulse of a CPS signal.
In another further embodiment, an exemplary method for preventing a reverse rotation of an engine according to an embodiment of the present invention further includes calculating a piston angle of the reversion-triggering cylinder at the time of occurrence of the reverse rotation of the engine, wherein whether the reverse rotation of the engine is occurring is determined on the basis of the piston angle of the reversion-triggering cylinder.
In a still further embodiment, the reverse rotation of the engine is determined to be occurring when the piston angle of the reversion-triggering cylinder lies in a range preceding TDC of the reversion-triggering cylinder.